Apparatus, method and computer readable recording medium for processing image information

ABSTRACT

An image processing apparatus, method and computer readable recording medium provided with a primary memory device and a secondary memory device both having image data memorized therein, in which said image data are input to said primary memory device, and including an external input data amount acquisition device acquiring the amount of said image data input to said primary memory device; an internal output data amount acquisition device acquiring the amount of said image data output from said primary memory device and input to said secondary memory device; a first difference data amount calculation device subtracting the amount of the data acquired by said internal output data amount acquisition device from the amount of the data acquired by said external input data amount acquisition device, and calculating first difference data amount by the subtraction; a memory access control device practicing the inputting and outputting of said image data with time sharing in said primary memory device, comparing said first difference data amount with a first value and a second value larger than said first value, stopping the processing of outputting said image data from said primary memory device to said secondary memory device when said first difference data amount reaches the value equal to or smaller than said first value, and starting again the processing of outputting said image data from said primary memory device to said secondary memory device when said first difference data amount reaches the value equal to or larger than said second value; and an error signal outputting device comparing said first difference data amount with a third value larger than said second value and a fourth value smaller than said first value, and outputting an error signal when said first difference data amount reaches the value equal to or larger than said third value or when said first difference data amount reaches the value equal to or smaller than said fourth value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus, method and computerreadable recording medium for performing a digital processing of imageinformation, and more particularly to an apparatus, method and computerreadable recording medium for performing a digital processing of imageinformation with a memory control system.

2. Discussion of the Background

With a advancement of a digitalization of an image processing apparatus,such as a copying machine and so forth, processing and editing of imagedata using an image memory to store image data has become popular.Exemplary devices for processing and editing image data include anelectronic sorter device and an image division device. An electronicsorter device memorizes image data of a plurality of original documentsin an image memory, and outputs a designated number of copies. Theelectronic sorter device eliminates the sorting of the copies andproduces a plurality of batches of copies of the original documents.

In order to achieve an electronic sort function, a copying apparatus isrequired to memorize all image data of a plurality of original documentsin an image memory. A copying apparatus includes a semiconductor memoryas a primary memory device (i.e., a main memory device) which isattached to a CPU (Central Processing Unit). However, because asemiconductor memory is comparatively expensive, a copying apparatusgenerally includes a secondary memory device (i.e., a supplementarymemory device), which supplements a memory capacity of the primarymemory device. The copying apparatus uses both primary and secondarymemory devices as an image memory. A secondary memory device includes adisk recording medium, such as a hard disk and a MO (magneto-opticaldisk), which are comparatively cheaper than a semiconductor memory.

A semiconductor memory is used as a buffer memory to absorb a differencebetween a transfer speed of image data of a secondary memory device andan input/output speed of image data of a copying apparatus. Asemiconductor memory is also used to output an image formed according toimage data by rotating the image with an address operation duringreading out of image data stored in a secondary memory device (i.e., animage rotation function). When an image data transfer speed of asecondary memory device is substantially high compared with an imagedata input/output speed of a copying apparatus, an input/output imagedata can be directly stored in a secondary memory device. In this way,such above-noted semiconductor memory is not required. Similarly, when acopying apparatus does not have an image rotation function, suchabove-noted semiconductor memory is also not required.

In a secondary memory device, data is sequentially stored. When thestored data is randomly read out so as to rotate an image, access speedis substantially lowered such that a speed of an image output, which acopying apparatus may require, may not be satisfied. For example, theinvention described in Japanese Patent Laid-Open Publication No.6-168183 includes a semiconductor memory with a correspondingly smallermemory capacity by controlling an image memory according to processingand editing functions. An apparatus according to the above-mentionedinvention includes a table to control a property of each semiconductormemory, which is a frame buffer memory, and a function to temporarilystore data, which is stored in a semiconductor memory, in a secondarymemory device.

According to the above-noted invention, when a frame buffer memory sizelarger than a remainder of a frame buffer memory size is required, datastored in a semiconductor memory is temporarily stored in a secondarymemory device referring to a property of a semiconductor memory in atable so as to secure a frame buffer memory size necessary for a newjob. A status of a job is described in the table, and whether or notdata stored in a semiconductor can be temporarily stored in a secondarymemory device is judged by the status.

An image division device outputs a plurality of images by dividing imagedata of an original document, which has been read out by being scannedonce by a scanner, into a plurality of images. The processing of animage division is performed by repeating operations in which an imagedata read out from an original document is temporarily stored in asemiconductor memory, the stored data is read out with an addressdesignated and is output to a printer at the same time.

Based on the above discussion, a digital copying machine having anelectronic sort function is often configured to include both asemiconductor memory and a secondary memory device and the capacity ofsuch a semiconductor memory typically equals the amount of datacorresponding to the largest possible transfer sheet output by thecopying machine. However, even if a semiconductor memory has a memorycapacity that can store data of the largest possible output transfersheet, it is very rare to execute an image rotation for a size of thelargest possible output transfer sheet. Further, when a secondary memorydevice has an access speed that is very much close to an image transferspeed corresponding to a copy speed of a copying machine, it absorbs aspeed difference, thereby eliminating a need of a semiconductor memory.

According to the above-noted devices, whether or not data can betemporarily stored in a secondary memory device is judged by comparing asize of a memory. Practically, it is sufficient to have a memory size inwhich transferred data is temporarily stored until it is output.However, because such devices compare an absolute volume of a memorysize, a memory used tends to be larger in a storage capacity so as tosecure a larger memory size.

In an image dividing device, image data read out by a single scan isrequired to be temporarily stored. However, current image dividingfunctions typically can not be applied to image data stored in a memorydevice other than a main memory device attached to a CPU. Therefore, acopying apparatus needs to include a semiconductor memory that is largeenough to store image data of the largest original document, which ascanner can scan in a single scan. This makes it difficult to downsize asemiconductor memory to be used.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-discussed andother problems and addresses the above-discussed and other problems.

The present invention advantageously provides a novel image processingapparatus and image forming apparatus, such as a copying machine, afacsimile and a printer; image processing methods suitably applied tothese apparatuses; and computer readable recording medium in which aprogram for the method to be executed by a computer is recorded. Theapparatuses, the methods, and the medium can be widely used supportingvarious kinds of systems by changing a value to be compared when avolume of a buffer memory is changed.

The present invention also advantageously provides the apparatuses, themethods, and the medium of a high productivity capable of a high speedaccess even with a relatively smaller buffer memory volume by: (i)reducing a volume of data exchanged with a secondary memory device, (ii)decreasing a memory processing time with the secondary memory device,and (iii) increasing the number of an original documents to bememorized.

According to the embodiment of the present invention, there is providedan image processing apparatus, method and computer readable recordingmedium provided with a primary memory device and a secondary memorydevice both having image data memorized therein, in which said imagedata are input to said primary memory device, and including an externalinput data amount acquisition device acquiring the amount of said imagedata input to said primary memory device; an internal output data amountacquisition device acquiring the amount of said image data output fromsaid primary memory device and input to said secondary memory device; afirst difference data amount calculation device subtracting the amountof the data acquired by said internal output data amount acquisitiondevice from the amount of the data acquired by said external input dataamount acquisition device, and calculating first difference data amountby the subtraction; a memory access control device practicing theinputting and outputting of said image data with time sharing in saidprimary memory device, comparing said first difference data amount witha first value and a second value larger than said first value, stoppingthe processing of outputting said image data from said primary memorydevice to said secondary memory device when said first difference dataamount reaches the value equal to or smaller than said first value, andstarting again the processing of outputting said image data from saidprimary memory device to said secondary memory device when said firstdifference data amount reaches the value equal to or larger than saidsecond value; and an error signal outputting device comparing said firstdifference data amount with a third value larger than said second valueand a fourth value smaller than said first value, and outputting anerror signal when said first difference data amount reaches the valueequal to or larger than said third value or when said first differencedata amount reaches the value equal to or smaller than said fourthvalue.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1 is a block diagram illustrating a basic construction andoperation of an image processing apparatus according to an embodiment ofthe present invention;

FIG. 2A explains a flow of image data from a primary memory device to asecondary memory device;

FIG. 2B explains a flow of image data from a secondary memory device toa primary memory device;

FIG. 3 illustrates an image processing apparatus common to first,second, and third embodiments of the present invention;

FIG. 4 illustrates an original document M shown in FIG. 3;

FIG. 5 is a timing chart showing synchronizing signals of image dataoutput from an IPU (Image Processing Unit) in FIG. 3;

FIG. 6 is a block diagram illustrating details of a memory section inFIG. 3;

FIG. 7 is a block diagram explaining a transfer of image data to asecondary memory device in a memory control section in FIG. 6;

FIGS. 8A and 8B explain a state of writing and reading out of data in animage memory when inputting an image data to a image memory;

FIGS. 9A and 9B explain a state of writing and reading out of data in animage memory when inputting an image data into image memory.

FIG. 10 is a flow chart explaining an image data input/output operation;

FIG. 11 explains a processing of outputting image data according to afirst embodiment of the present invention;

FIG. 12 explains a construction of an image processing apparatusaccording to a second embodiment of the present invention;

FIGS. 13A, 13B, and 13C explain a processing of renewing a set valueaccording to the second embodiment of the present invention;

FIG. 14 explains operations according to the second embodiment of thepresent invention;

FIG. 15 is a block diagram showing a memory section of an imageprocessing apparatus;

FIG. 16 explains a composition of a memory control section;

FIGS. 17A and 17B is a flow chart explaining a cut out image operation;and

FIG. 18 is a flow chart explaining a processing of an image dividing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, and moreparticularly to FIG. 1 thereof there is illustrated an image processingapparatus 101 according to the present invention. The image processingapparatus 101 constitutes a copying apparatus in combination with aninput device 102, such as a scanner, a printing section to perform aprinting, and an output device 103, such as a plotter.

The image processing apparatus 101 includes an image input/outputsection 104, a primary memory device 105, a compression/decompressionsection 106, and a secondary memory device 107. The primary memorydevice 105 stores image data A input from the input device 102 throughthe image input/output section 104. The stored image data is output tothe secondary memory device 107 (image data B). The image data iscompressed by the compression/decompression section 106 and is stored inthe secondary memory device 107.

The image data stored in the secondary memory device 107 is read outwhen necessary (image data D). The image data read out is decompressedby the compression/decompression section 106 and is input to the primarymemory device 105. The image data is processed and edited by the primarymemory device 105, and is output to the output device 103 (image data C)through the image input/output section 104. The primary memory device105 illustrated in FIG. 1 includes a semiconductor memory. The secondarymemory device includes a hard disk drive, which can store larger amountof data than a semiconductor memory.

When image data is input to the secondary memory device 107 from theprimary memory device 105, the image data A, input by the input device102, is input to the primary memory device 105 through the imageinput/output section 104, as illustrated in FIG. 2A, and is thenbit-mapped. That is, the image data A is stored in the primary memorydevice 105 in a condition that a line formed by arranging image data ofeach pixel in a main scanning direction in image reading (hereinafterreferred to as a line) is arranged parallel to a sub-scanning direction.

The image data A stored in the primary memory device 105 is read outfrom the primary memory device 105 as the image data B. The image data Bis compressed by the compression/decompression section 106 and is thenstored in the secondary memory device 107. The above-described imagedata input operation is performed, for example, when the primary memorydevice 105 is used as a buffer to absorb a difference of transfer speedof image data between the input device 102 and the secondary memorydevice 107.

In operations shown in FIG. 1, the image data A is input to the primarymemory device 105 and is stored. In parallel with the storage, the imagedata B is output from the primary memory device 105. During theoperation, it may happen that an amount of the image data A becomeslarger than that of the image data B in the primary memory device 105due to a difference between a transfer speed of the image data A to theprimary memory device 105 and a transfer speed of the image data B tothe compression/decompression section 106. When the amount of the imagedata A becomes larger than that of the image data B, it may happen thatimage data, in the primary memory device 105 which has not been output,may be lost by being overwritten by the newly input image data A.According to a first embodiment of the present invention, when imagedata is input, an error signal is generated to avoid part of image databeing lost, when the amount of the image data A becomes larger than thatof the image data B by a predetermined amount of data or more.

When image data is input to the primary memory device 105 from thesecondary memory device 107, the image data D read out from thesecondary memory device 107 is stored in the primary memory device 105after it has been decompressed by the compression/decompression section106. The image data D is read out from the primary memory device 105 andis output to the output device 103 through the image input/outputsection 104 as the image data C. The above-described image data outputoperation is performed, for example, when printing image data stored inthe secondary memory device 107 by storing a each part of the image datain the primary memory device 105.

In operations shown in FIG. 2B, it may happen that an amount of theimage data D becomes larger than that of the image data C in the primarymemory device 105 due to a difference between a transfer speed of theimage data D to the primary memory device 105 and a transfer speed ofthe image data C to the image input/output section 104. When the amountof the image data D becomes larger than that of the image data C, it mayhappen that image data, in the primary memory device 105 which has notbeen output, may be lost by being overwritten by the newly input imagedata D. According to a first embodiment of the present invention, whenimage data is output, an error signal is generated to avoid part ofimage data being lost, when the amount of the image data D becomeslarger than that of the image data C by a predetermined amount of dataor more.

According to a second embodiment of the present invention which will bedescribed below, a setting of the predetermined amount of data describedin the first embodiment of the present invention can be renewedaccording to a input/output state of image data in the primary memorydevice 105. Timing used to generate the error signal can be adjustedaccording to a state of image processing so that the primary memorydevice 107 can be efficiently used.

Further, according to a third embodiment of the present invention whichwill be described below, in an image data output operation, the imagedata D is made to be part of data for image data of one originaldocument. With this arrangement, the primary memory device can bedownsized or it can be possible that part of a memory capacity of theprimary memory device 105 is used for storing image data and remainingpart of the memory capacity of the primary memory device 105 is used forprocessing and editing image data.

First Embodiment

An exemplary embodiment of an image processing apparatus according to afirst embodiment of the present invention is a digital multi-functionalimage forming apparatus (hereinafter referred to as an image formingapparatus), which includes an image reading section 310 to read anoriginal document, an image forming section 330 to form an image on atransfer sheet and discharge it, and a FAX section. In the image readingsection 310, an image of the original document M disposed on a platen311 is read. The platen 311 has a size of, for example, 12-inches inlength and 17-inches in width. The original document M is disposed onthe platen 311 by adjusting a standard part S thereof to the most upperend and right end of the platen 311. The platen 311 includes a sensor(not shown) to detect a position of the original document M.

An exposing lamp 317 scans and exposes the original document M by movingunder the platen 311. Reflected light from the original document M isled to a CCD (Charged-Coupled Device) sensor 313 by a reflected lightmirror 314. The light is then converted to an analog electric signal bythe CCD sensor 313 according to an intensity of the light and is inputto an IPU (Image Processing Unit). The IPU 312 generate an image data bytransforming the analog electric signal to a digital signal of 8 bits.The IPU 312 performs processing including a shading compensation, amagnification/reduction processing and a dither processing. The IPU 312transmits each line of the processed image data to a memory section 322or to a writing section 331 of the image forming section 330 through aselection section 321 together with a synchronizing signal.

A scanner control section 316 inputs detecting signal “a” from varioussensors (not shown) in order to perform the above-described process ofthe image reading section 310. The scanner control section 316 controlsa driving motor (not shown) to drive the CCD sensor 313 according to thedetecting signal “a”, and also sets various parameters for the IPU 312.

In the image forming section 330, a surface of a photoconductive element337, which rotates in a clockwise direction at a fixed speed, isuniformly charged by a charging device 336. In the writing section 331,a latent image is formed on the surface of the photoconductive element337 by laser beam light modulated according to image data. The latentimage is developed into a toner image with toner in a developing device338. The toner image is transferred onto a transfer sheet by a transfercharger 341.

Residual toner remaining on the surface of the photoconductive element337 is removed by a cleaning device 334, and a residual charge thereofis removed by a discharging device 335. The writing section 331 includesa known laser writing system including a laser diode, a polygon mirror,a polygon motor, an fθ lens, and a synchronization detecting element(not shown).

A transfer sheet (not shown) set in a sheet feeding tray 344 is conveyedby a sheet feeding roller 343, and is then conveyed by a registrationroller 342 so as to be in register with a toner image on a surface ofthe photoconductive element 337. The transfer sheet is separated fromthe photoconductive element 337 by a separation charger 340 after thetransfer charger 341 has transferred the toner image onto it. The tonerimage is fixed by a fixing device 333, and is discharged to an exit tray332 by a sheet discharging roller 339.

A printer control section 345 inputs detecting signal “a” from varioussensors (not shown) in order to perform the above-described process ofthe image forming section 330. The printer control section 345 controlsa driving motor (not shown) to drive the writing section 331 accordingto the detecting signal “a”.

The image forming apparatus illustrated in FIG. 1 includes a systemcontrol section 323, an operation unit 360, the memory section 322, andthe FAX section 350. An instruction to the system control section 323 isgiven through a key input to the operation unit 360. When a key input isdone, the system control section 323 detects a content of instructionsfor copying. According to the content of the instructions, the systemcontrol section 323 sets various parameters for the memory section 322,the scanner control section 316 of the image reading section 310, andthe printer control section 345 of the image forming section 330 or itprovides these sections with instructions to execute respective process.The system control section 323 provides instructions to display a stateof a whole system on a screen of a display provided in the operationunit 360.

The memory section 322 inputs image data of an original document fromthe IPU 312 through the selection section 321 and stores it. The storedimage data is used for a copying application for editing and processingof an image, such as a repeat copy, an image rotation copy, anelectronic sorting, an image division, and so forth. The memory section322 is also used as a buffer memory to temporarily store binary imagedata, which the FAX section 350 received. A data storing operation inthe memory section 322 is controlled by the system control section 323.

The selection section 321 selects a source of image data, to be used foran image forming in the image forming section 330, either from the imagereading section 310 or the memory section 322. The selection section 321also selects a source of image data to be stored in the memory section322 either from the image reading section 310 or the FAX section 350.

Image data output from the IPU 312 synchronizes with varioussynchronizing signals shown in FIG. 5. A frame gate signal (/FGATE)indicates an image effective range of an image area in a sub-scanningdirection. Image data is effective during the frame gate signal (/FGATE)when at a low level (active-low). The frame gate signal (/FGATE) isasserted or negated with a trailing edge of a line synchronizing signal(/LSYNC). The line synchronizing signal (/LSYNC) remains asserted duringa predetermined number of a pixel clock (PCLK) counting from a leadingedge of the pixel clock (PCLK). After a rise of the line synchronizingsignal (LSYNC), a predetermined number of clock signals are generated,and then an image data in a main scanning direction becomes effective.

The IPU 312 outputs one image data for one cycle of the pixel clock(PCLK). The one image data is one of image data of an original documentdivided into a equivalent of 400 dpi in a main scanning direction and asub-scanning direction from the standard part S in FIG. 4. The dividedimage data is sent out as a raster type data heading the image datapositioned at the standard part S. An effective range of an image datain a sub-scanning direction is generally decided according to a size ofa transfer sheet.

The FAX section 350 carries out a binary compression of an image databased on G3 and G4 FAX data transmission regulations according to aninstruction from the system control section 323 and transfers thecompressed image data to a telephone line. Data transferred to the FAXsection 350 from a telephone line is decompressed to a binary imagedata, and is transferred to the writing section 331 of the image formingsection 330 to form a visual image.

As illustrated in FIG. 6, the memory section 322 includes a memorycontrol section 602, an image input/output section 601 controlled by thememory control section 602, a compression/decompression section 604, animage memory, which is a primary memory device and includes asemiconductor memory, and a hard disk drive (HD) 605 as a secondarymemory device that exchanges data with the compression/decompressionsection 604. According to the embodiment of the present invention, theimage input/output section 601, the compression/decompression section604, and the memory control section 602 include a CPU and logiccircuits.

According to the first embodiment of the present invention, the imagememory 603 includes a semiconductor memory element, such as a DRAM(Dynamic Random Access Memory). A volume of the memory is set to be 2Mbyte. That is, the sum total of the memory volume is 400 DPI (Dot PerInch), which is equivalent to a binary image data of A4 size paper. Thehard disk drive 605 is a secondary memory device, which includes amagnetic recording medium and has a memory capacity larger than that ofthe image memory 603. An information recording device, such as amagneto-optical recording device can also be used as a secondary memorydevice if the device can store data in volume having a certain level ofdata access speed.

The image input/output section 601 receives a command from the memorycontrol section 602 by communicating with it and makes operationsettings according to the command. The image input/out section 601transmits status information to the memory control section 602 to informa state of input/output of an image. When the image input/output section601 receives a command of an image input from the memory control section602, the image input/output section 601 inputs image data transmittedfrom the IPU 312 (indicated by a dotted line in FIG. 6) line-by-linetogether with synchronizing signals (an input frame gate signal, aninput line synchronizing signal, and an input pixel synchronizingsignal), which are used to decide a time to input an image. According tothe input pixel synchronizing signal, the image input/output section 601outputs input image data line-by-line as memory data of 8-pixel unittogether with an input/output memory access signal “c” to the memorycontrol section 602 whenever necessary.

When an image data is input, the image input/output section 601 acquiresa volume of input data and outputs the acquired data volume to thememory control section 602. According to the embodiment of the presentinvention, a volume of image data is acquired by counting the number oflines of input/output image data. The number of lines counted is outputto the memory control section 602.

In an image processing apparatus, which outputs and inputs line-by-lineimage data, a volume of an image data can be acquired, for example, bycounting an input line synchronizing signal. Therefore, the apparatusdoes not need to have an exclusive device separately to acquire a volumeof image data, which is advantageous for avoiding an increase in thenumber of parts used.

When the image input/output section 601 receives a command for an imageoutput, it outputs image data, input through the memory control section602, to the writing section 331 in synchronization with synchronizingsignals (an output frame gate signal, an output line synchronizingsignal and an output pixel synchronizing signal), which are used todecide a time to output an image.

The compression/decompression section 604 receives a command from thememory control section 602 by communicating with it and makes operationsettings according to the command. Further, thecompression/decompression section 604 transmits status information tothe memory control section 602 to inform a state of compression anddecompression processing. When the compression/decompression section 604receives a command of compression from the memory control section 602,the compression/decompression section 604 outputs a transfer memoryaccess signal “d” to the memory control section 602, and receives atransfer memory access permission signal “e” from the memory controlsection 602.

When the transfer memory access permission signal “e” is active, thecompression/decompression section 604 receives image data and compressesit, which is stored in the hard disk drive 605 as a compressed data.During the operation, the compression/decompression section 604 acquiresa volume of data of an image to be compressed and outputs the acquireddata to the memory control section 602. A volume of data is acquired bycounting the number of lines of image data (the number of lines of imagedata output from the image memory 603).

When the compression/decompression section 604 received a command ofdecompression, it reads out compressed data stored in the hard diskdrive 605, and decompresses the data. The decompressed date is output tothe memory control section 602. The compression/decompression section604 exchanges a transfer memory access signal “d” and a transfer memoryaccess permission signal “e” with the memory control section 602.

As described above, data volume is reduced by arranging thecompression/decompression section 604 between the hard disk drive 605and the image memory 603, which reduces a data volume to be stored inthe hard disk drive 605 enabling the hard disk drive 605 to store alarger volume of data.

The memory control section 602 receives a command from the systemcontrol section 323 by communicating with it and makes operationsettings according to the command. The memory control section 602transmits status information to the system control section 323 to informa state of the memory section 322.

The system control section 323 outputs operation commands including animage input, an image output, a compression and a decompression. Thecommands of the image input and output are transmitted to the imageinput/output section 601, while the compression and decompressioncommands are transmitted to the compression/decompression section 604.

As shown in FIG. 7, the memory control section 602 includes a differencecalculation section 701, a line setting section 702, a differencecomparison section 703, a demand mask section 704, an arbiter 705, aninput/output image address counter 706, transfer image address counter707, an address selector 708, and an access control circuit 709.

When the image memory 603 is used as a buffer memory for inputting imagedata, the difference calculation section 701 calculates a difference inthe number of lines by subtracting the number of lines of image data C2output from the image memory 603 (output line number) from the number oflines of image data C1 input to the image memory 603 (input linenumber).

The line setting section 702 receives the number of lines, which iscompared with a difference in the number of lines in the differencecomparison section 703, from the system control section 323 and sets thenumber of lines in the memory control section 602. The number of lines(set line number) can be freely set.

By having the line setting section 702, the number of lines comparedwith a difference in the number of lines can be changed according tosystem requirements, such as a line period of input image data, atransfer speed with the hard disk drive 605 and so forth. Accordingly,the apparatus can be widely used supporting various kinds of systems.

The difference comparison section 703 compares the difference in thenumber of lines calculated by the difference calculation section 701with the number of lines set by the line setting section 702. Accordingto a comparison result obtained at the difference comparison section703, the demand mask section 704 masks a transfer memory access signal“d” (makes the transfer memory access signal disabled). The arbiter 705outputs a transfer memory access permission signal “e” so that thecompression/decompression section 604 can access the image memory 603.The transfer memory access permission signal “e” is output under thecondition that an address comparison signal is active and that aninput/output memory access signal “c” is non-active.

The input/output image address counter 706 counts up an addressaccording to an input/output memory access signal “c” and outputs amemory address of 22 bits to the address selector 708 showing an addresswhen an image data is stored in the image memory 603. The memory addressin the address selector 708 is once initialized when a memory accessstarts.

The transfer image address counter 707 counts up an address according toa transfer memory access permission signal “e” and outputs a memoryaddress of 22 bits to the address selector 708 showing an address whenan image data is stored in the image memory 603. The memory address inthe address selector 708 is once initialized when a memory accessstarts.

An address of either an input image or a transfer image is selected bythe arbiter 705 in the address selector 708. The access control circuit709 divides an address of a DRAM included in the image memory 603 intorow address and a column address corresponding to a physical addressselected in the address selector 708, and outputs them to an address busof 11 bits. The access control circuit 709 also outputs DRAM controlsignals (Row Address Stroke, Column Address Stroke, Write Enable)according to an access start signal from the arbiter 705.

A control of the image memory 603 by the memory control section 602 whenan image data is input to or output from the image memory 603 will bedescribed below.

1. Inputting Image Data

When inputting image data, for example, from a scanner of the imagereading section 310, at the memory control section 602, the differencecalculation section 701 subtracts the number of external output lines C2from the number of internal input lines C1 input into the image memory603 so as to obtain the number of difference. The difference calculationsection 703 compares the number of difference with the predeterminedfirst, second, third and fourth values.

The memory control section 602 controls the image input/output section601 and the compression/decompression section 604, and stops the processof outputting image data from the image memory 603 when the number ofdifference reaches a value not greater than the first value. Further,the memory control section 602 resumes the process of outputting theimage data from the image memory 603 when the number of differencereaches a value not smaller that the second value. Furthermore, thememory control section 602 outputs an error signal when the number ofdifference reaches a value not smaller than the third value or a valuenot greater than the fourth value.

The relationship of the first, second, third, and fourth values in sizeis expressed as follows;third value>second value>first value>fourth value

The first to fourth values used in the comparison with the number ofdifference are set at the difference calculation section 703. Thesevalues are changeable as necessary.

Now, the process of outputting an error signal and the process ofstopping and resuming image data transfer performed according to thefirst to fourth values are described.

(1) Process for Outputting an Error Signal

The demand mask section 704, the arbiter 705, the input/output addresscounter 706, the transfer image address counter 707, the address counter708 and the access control section 709 are operated on a basis of thejudgment of the difference comparison section 703. The access controlcircuit 709 generates a control signal by the operation based on thejudgement of the difference comparison section 703. The control signalis output via an address bus and a control signal line, and controls theimage input/output section 601 and the compression/ decompressionsection 604.

The difference comparison section 703 compares the number of differencewith the third value, and outputs an error signal “f” when the number ofdifference reaches a value not smaller than the third value. The errorsignal “f” is used as a control signal of the image processing apparatus101 and prevents the image data stored in the image memory 603 frombeing overwritten to be lost by the image data newly input.

The difference calculation section 703 compares the number of difference(C1−C2) and the number of set lines (first value V1, second value V2,third value V3, fourth value V4) output by the line setting section 702.When either of the following conditions is satisfied, the error signal“f” is output:C 1−C 2≧V 3  [1]C 1−C 2≦V 4  [2]

The operation of outputting the error signal “f” when the condition [1]is satisfied is made for preventing the image data stored in the imagememory 603 from being lost. This operation can be realized, for example,by inputting the error signal “f” into the operation unit 360 so as todisplay a message indicating that the error has occurred in a displayscreen of the operation unit 360. According to this configuration, theoperator can recognize, based upon the display in the display screen,that the image memory 603 can not store additional image data any more,and thereby can stop the whole system of the image processing apparatus101, or the error signal “f” can be output to the controller of thewhole system so as to cause the controller to temporarily stop thereading operation of the image reading section 310 to thereby preventthe image data from being lost as a result of being overwritten.

Alternatively, the error signal “f” can be input into the scannercontrol section 316 so as to stop the scanner of the image readingsection 310 with the error signal “f”, and thereby input of image datainto the image memory 603 can be automatically stopped. Furtheralternatively, the scanner control section 316 may be controlled suchthat the reading speed of the scanner of the image reading section 310is decreased.

The operation of outputting the error signal “f” when the condition [2]is met is for outputting information informing that no image data fortransferring to the hard disk drive 605 exists in the image memory 603.Further, when the fourth value is set to zero, the controllercontrolling the whole part of the image processing apparatus 101 isinformed of that a system error, in which the number of difference iscalculated to be a negative number, has occurred.

(2) Process for Stopping and Resuming Image Data Transfer

The difference calculation section 703 compares the number of externalinput lines C1 and the number of internal output lines C2, and when thefollowing condition is satisfied:C 1−C 2≦v 1  [3]the transfer demand mask signal “h” to be output to the demand masksection 704 is made active. The demand mask signal “h” output by thedifference comparison section 703 is input into the demand mask section704.

At the same time, the compression/decompression section 604 inputs intothe demand mask section 704 a transfer access demand signal “d”. Thedemand mask section 704 determines if the transfer demand mask signal“h” is active. When the transfer demand mask signal “h” is active, thedemand mask section 704 masks (disables) the transfer access demandsignal “d”. By this process, when the transfer access demand signal “d”is masked, the process of transferring image data from the image memory603 to the hard disk drive 605 is stopped.

After the process of transferring image data from the image memory 603to the hard disk drive 605 is stopped, the difference calculationsection 703 compares the number of external input lines C1 and thenumber of internal output lines C2. When the following condition issatisfied:C 1−C 2≧V 2  [4],the masking of the transfer access demand signal “d” is released. Thetransfer access demand signal “d” is then input into the arbiter 705.

At this time, to the arbiter 705, the input/output memory access signal“c” output by the image input/output section 601 is input. The arbiter705 outputs a transfer access approval signal “e” to thecompression/decompression section 604 in response to the transfer accessdemand signal “d”, when the input/output memory access signal “c” is notactive and the transfer demand access signal “h” input via the demandmask section 704 is active. By the processes describe above, the processof transferring image date from the image memory 603 to the hard diskdrive 605 is resumed.

Further, at this time, the arbiter 705 counts up the input/output imageaddress counter 706 in accordance with the input/output memory accesssignal “c”, and counts up the transfer image address counter 707 inaccordance with the transfer access approval signal “e”. Each of thecounted numbers is input into the address selector 708, and the addresscounter 708 selects either of the addresses of the input image or thetransfer image according to the input counted number and the signal “f”output by the arbiter 705. With this configuration, according to thepreferred embodiment of the present invention, the processes of stoppingand resuming the operation of the memory control section 602 can beperformed in parallel by time-sharing.

When inputting image data into the image memory 603, immediately afterstarting inputting of image data, the volume of image data stored in theimage memory 603 is zero. At this time, if the process of transferringimage data from the image memory 603 to the hard disk drive 605 isstarted, the image data for transfer to the hard disk drive 605 does notexist in the image memory 603 such that the condition [2] is satisfied,and thereby the transfer of image data may be stopped.

Therefore, in the image processing apparatus 101 according to thepreferred embodiment of the present invention, before the memory controlsection 602 outputs image data from the image memory 603 to the harddisk drive 605, the memory control section 602 inputs into the imagememory 603 image data having the volume corresponding to the firstvalue. Further, the memory control section 602 controls the differencecalculation section 703 so as to output the error signal “f” only whenthe process of outputting image data from the image memory 603 to thehard disk drive 605 is being executed.

Now, referring to FIGS. 8(a) and 8(b), the operation of the image memory603 when inputting image data, according to the preferred embodiment 1,is described. FIG. 8(a) illustrates the total volume of image dataaccessing the image memory 603 in the midst of the image inputtingoperation, and FIG. 8(b) illustrates a state of the address beingaccessed at the image memory 603. The flows of image data indicated by Aand B in FIGS. 8(a) and 8(b) correspond to the image data flowsindicated by A and B in FIG. 1.

The difference calculation section 701 calculates the number ofdifference between the number of external input lines C1 expressing thedata volume of image data A in the number of lines and the number ofoutput lines C2 expressing the data volume of image data B in the numberof lines, and outputs the error signal “f” when the value of the numberof difference exceeds V3. By this operation, an over-running of theaddress, if occurring in the second round of image data inputting intothe image memory 603 for either of the following reasons, can berecognized in an early stage so as to be stopped when:

1) The transfer to the secondary memory device 107 is extremely slowwhen compared with the inputting speed of image data.

2) The buffer memory size is not appropriate.

3) The process of transfer is abnormal.

The above can be realized in a relatively simple configuration becausedata volume of image data is managed based upon the difference betweenthe number of input and output lines.

In the preferred embodiment 1, despite only a 2M bytes semiconductormemory being used in the image memory 603, 4M bytes image data is inputinto the memory section 322. Further, because the address counters 706and 707 are configured so as to return to zero when the address of thehighest order is accessed, if the volume of accessing data exceeds 2Mbytes, the same address is accessed two times.

Further, when the value of the number of difference calculated by thedifference calculation section 701 is not greater than V1, the processof transferring image data from the image memory 603 to the hard diskdrive 605 is stopped. When the value of the number of difference is notsmaller than V2, the transfer process is resumed. When the value of thenumber of difference is not greater than V4, the error signal “f” isoutput.

As described above, according to the preferred embodiment 1, the errorsignal “f” is sent to the system control section 323 when the condition[1] or [2] is satisfied when inputting an image. By this operation, suchtrouble as erroneously setting the predetermined values used forcomparison or overrunning of a transfer process by an input process dueto a system error can be found in an early stage so as to be stopped.

Next, the operation of the whole part of the memory section 322according to the preferred embodiment 1 is described.

According to an image inputting instruction by the system controlsection 323, the memory control section 602 is initialized so as to bein an image data waiting state. Further, by the operation of the scannerof the image reading section 310, image data is input into the memorysection 322. The input image data is input into the image memory 603 andis once written into the image memory 603. The number of the input linesC1 of the written image data is counted by the image input/outputsection 601 and is input into the memory control section 602.

The compression/decompression section 604 receives the image transfercommand output by the memory control section 602 and outputs thetransfer access demand signal “d”. At this time, the transfer accessdemand signal “d” is masked by the demand mask section 704 at the memorycontrol section 602, and memory access to the image memory 603 is notperformed. Upon completion of the process of bit-mapping the image datainto the image memory 603 for one line of the image data input from theimage input/output section 601, masking of the transfer access demandsignal “d” is released. Then, the operation of reading the image datastored in the image memory 603 and transferring the image data to thecompression/decompression section 604 is started. Further, during theoperation of inputting/outputting image data into/from the image memory603, the difference calculation section 701 calculates the differencebetween the number of external input lines C1 and the number of internaloutput lines C2, and compares the difference with each of the first tofourth values. Then, as described above, according to the result of thecomparison, an error signal is output, the transfer access demand masksignal “d” is masked, or masking of the transfer access demand signal“d” is released.

2. Outputting Image Data

Now, the operation of the image processing apparatus 101 when outputtingimage data is described. Description for common parts of the operationwith the image inputting operation described above is partly omitted.When outputting image data to the image forming section 330, at thememory control section 602, the difference calculation section 701subtracts the number of external output lines C2′, output from the imagememory 603 to the image forming section 330, from the number of internalinput lines C1′, input into the image memory section 603 from the harddisk drive 605, to obtain the number of difference. The differencecalculation section 703 compares the number of difference withpredetermined fifth, sixth, seventh, and eighth values.

The memory control section 602 controls the image input/output section601 and the compression/decompression section 604, and when the numberof difference reaches a value not greater than the fifth value, theoperation of outputting image data from the image memory 603 is stopped.Further, the memory control section 602 resumes the operation ofoutputting image data from the image memory 603 when the number ofdifference reaches a value not smaller than the sixth value.Furthermore, when the number of difference reaches a value not smallerthan the seventh value or a value not greater than the eighth value, thememory control section 602 outputs an error signal.

The relationship of the fifth, sixth, seventh, and eighth values in sizeis expressed as follows:seventh value>sixth value>fifth value>eighth value

The fifth to eighth values used in comparison with the number ofdifference are set at the difference calculation section 703 by the linesetting section 318. These predetermined values are changeable asnecessary.

Now, the processes of outputting an error signal and stopping andresuming image data transfer, performed according to the fifth to eighthvalues, are described.

(1) Process of Outputting an Error Signal

The demand mask section 704, the arbiter 705, the input/output addresscounter 706, the transfer image address counter 707, the address counter708 and the access control section 709 are operated on a basis of thejudgment of the difference comparison section 703. The access controlcircuit 709 generates a control signal by the operation based on thejudgement of the difference comparison section 703. The control signalis output via an address bus and a control signal line, and controls theimage input/output section 601 and the compression/decompression section604.

The difference comparison section 703 compares the number of differencewith the seventh value, and outputs the error signal “f” when thenumber, of difference reaches a value not smaller than the seventhvalue. The error signal “f” is used as a control signal of the imageprocessing apparatus 101 and prevents the image data stored in the imagememory 603 from being overwritten to be lost by the image data newlyinput.

The difference calculation section 703 compares the number of difference(C1′−C2′) output by the difference calculation section 701 and thenumber of set lines (fifth value V5, sixth value V6, seventh value V7,eighth value V8) output by the line setting section 702. When either ofthe following conditions is met, the error signal “f” is output:C 1′−C 2′≧V 7  [5]C 1′−C′2′≦V 8  [6]

The operation of outputting the error signal “f” when the condition [5]is met is made for preventing the image data stored in the image memory603 from being lost. The operation of outputting the error signal “f”when the condition [6] is met is made for outputting informationinforming that sufficient image data for transferring to the imageforming section 330 does not exist in the image memory 603.

(2) Process of Stopping and Resuming Image Data Transfer

The difference calculation section 703 compares the number of internalinput lines C1′ and the number of external output lines C2′, and whenthe following condition is satisfied:

 C 1′−C 2′≦V 5  [7]

the transfer demand mask signal “h” to be output to the demand masksection 704 is made active. The transfer demand mask signal “h” outputby the difference comparison section 703 is input into the demand masksection 704.

At the same time, the compression/decompression section 604 inputs intothe demand mask section 704 a transfer access demand signal “d”. Thedemand mask section 704 determines if the transfer demand mask signal“h” is active. When the transfer demand mask signal “h” is active, thedemand mask section 704 masks (disables) the transfer access demandsignal d. By this process, when the transfer access demand signal “d” ismasked, the process of transferring image data from the image memory 603to the hard disk drive 605 is stopped.

After the process in which image data are transferred from the imagememory 603 to the hard disk drive 605 is finished, the differencecomparison section 703 compares the input line number C1′ with theoutput line number C2′. When the following condition:C 1′−C 2′≧V 6  [8]is satisfied, the mask of the transfer access demand signal “d” iscanceled. The transfer access demand signal “d” in which the mask hasbeen canceled is input to the arbiter 705.

In this case, the input/output memory access signal “c” input from theimage input/output section 601 has been input to the arbiter 705. Whenthe input/output memory access signal “c” is inactive and the transferdemand mask signal “h” input via the demand mask section 704 is active,the transfer access permission signal “e” is output to thecompression/decompression section 604 according to the transfer accessdemand signal “d”. By performing the above-identified process, theprocess in which image data is transferred from the image memory 603 tothe hard disk drive 605 is started again.

When image data are output from the image memory 603, the quantity ofimage data, which have been stored in the image memory 603, are zerosoon after the image data start to be input from the hard disk drive 605to the image memory 603. At this point, when the process in which imagedata are transferred from the image memory 603 to the image formingsection 330 is started, it may occur a shortage of the image data, whichare to be transferred to the image forming section 330, in the imagememory 603. Therefore, there is a possibility that the condition 7 issatisfied and the image data transfer is stopped.

In order to avoid such a problem, in the image forming apparatus of thepresent embodiment image data whose quantity is equal to the fifth valueare preliminarily input from the hard disk drive 305 to the image memory603 before image data are output from the image memory 603 to the imageforming section 330. In addition, the difference comparison section 703is controlled so that an error signal is output only when the process inwhich image data are output from the image memory 603 to the imageforming section 330 is performed.

Then image data inputting operations in the first embodiment will beexplained referring to FIGS. 9A and 9B. FIG. 9A illustrates the totalamount of image data being accessed to the image memory 603 during theimage input operations. FIG. 9B illustrates a state of the accessedaddress in the image memory 603. The flows of image data indicated by Cand D in FIGS. 9A and 9B correspond to the flows of image data indicatedby D and C in FIG. 1, respectively.

The difference calculation section 701 calculates the line numberdifference between the input line number C1′ and the output line numberC2′. When the line number difference is greater than V7, an error signal“f” is output. By performing this operation, an address overtakingproblem can be rapidly found when the address overtaking problem occursduring the second cycle, for example, for the following reasons that:

(1) the speed of image data transfer to the image forming section isextremely slow compared to the input speed of image data input from thesecondary memory device;

(2) the buffer memory quantity is not adequate; and

(3) the image data transfer process is in an abnormal state.

In addition, since the quantity of image data is controlled using theline number difference, the configuration of the section can besimplified.

Next, the above-mentioned processes in the first embodiment will beexplained referring to the flowcharts as shown in FIGS. 10 and 11. FIG.10 is a flowchart for explaining the process in which image data areinput in the image processing apparatus. FIG. 11 is a flowchart forexplaining the process in which image data are output in the imageprocessing apparatus.

As illustrated in FIG. 10, when image data are input, the memory controlsection 602 at first inputs an external input line number C1 (StepS1001), and then inputs an internal output line number C2 (Step S1002).Then a value ΔC is determined by subtracting the internal output linenumber C2 from the external input line number C1 (Step S1003).

Then, the difference comparison section 703 judges whether ΔC is notless than V3 (Step S1004). When ΔC is not less than V3 (i.e., “Yes” inStep S1004), an error signal is output (Step 1006). On the contrary,when ΔC is less than V3 (i.e., “No” in Step S1004), the differencecomparison section 703 judges whether ΔC is not greater than the fourthvalue V4 (Step S1005).

When ΔC is not greater than V4 (i.e., “Yes” in Step S1005), thedifference comparison section 703 outputs an error signal (Step S1006).On the contrary, when ΔC is greater than V4 (i.e., “No” in Step S1005),the memory control section 602 judges whether the operation ofoutputting image data to the hard disk drive 605 is performed (StepS1007). When the image data outputting operation is not performed (i.e.,“No” in Step S1007), it is judged whether the memory access permissionsignal should be output (Step S1012).

On the contrary, when the image data outputting operation is performed(i.e., “Yes” in Step S1007), it is judged whether ΔC is not less than V1(Step S1008). When ΔC is not less than V1 (i.e., “Yes” in Step S1008), atransfer memory access mask signal is made to be active so as to stop anoutput of image data (Step S1010). When ΔC is not greater than v1 (“No”in Step S1008), it is judged whether ΔC is not less than v2 (StepS1009). When ΔC is not less than v2 (“Yes” in Step S1009), it is judgedwhether the memory access permission signal should be output withoutmasking the transfer memory access signal (Step S1012).

In addition, when ΔC is less than V2 (i.e., “No” in Step S1009), theprocess of making the transfer demand mask signal active and the processof masking the transfer demand signal are continuously performed (StepsS1010 and S1011). When the transfer demand signal is input to the memorycontrol section 602 without being masked, the memory control section 602judges whether the condition such that the transfer access permissionsignal can be output according to the transfer access demand signal issatisfied (Step S1012).

When the condition is satisfied (i.e., “Yes” in Step S1012), the memorycontrol section 602 outputs the transfer access permission signal (StepS1013). On the contrary, the condition is not satisfied (i.e., “No” inStep S1012), the input/output address counter 706 and the transfer imageaddress counter 707 perform counting according to the process (StepS1014). Then the address selector 708 selects either the address of theinput image or the address of the transfer image (Step S1015), and asignal for controlling the image memory 603 is output via control signalline (Step S1016).

Next, the image data outputting process will be explained referring tothe flowchart as shown in FIG. 11. Since the processes in the flowchartin FIG. 11 include the processes that have been explained referring toFIG. 10, only the processes different from the processes in theflowchart in FIG. 10 will be hereinafter explained, and explanation ofthe similar processes will be sometimes omitted.

As shown in the flowchart in FIG. 11, when the image data are output,the memory control section 602 at first inputs an internal input linenumber C1′, which represents the quantity of image data input by thehard disk drive 605 to the image memory 603 (Step S1101), and thenoutputs an external output line number C2′, which represents thequantity of image data output from the image memory 603 to the imageforming section 330 (Step S1102). Then a value ΔC′ is determined bysubtracting the external output line number C2′ from the internal inputline number C1′ (Step S1103).

Then, the difference comparison section 703 judges whether ΔC′ is notless than V7 (Step S1104). When ΔC′ is not less than V7 (i.e., “Yes” inStep S1104), an error signal is output (Step 1106). On the contrary,when ΔC′ is less than V7 (i.e., “No” in Step S1104), the differencecomparison section judges whether ΔC′ is not greater than the eighthvalue V8 (Step S1105).

When ΔC′ is not greater than V8 (i.e., “Yes” in Step S1105), thedifference comparison section 703 outputs an error signal (Step S1106).On the contrary, when ΔC′ is greater than V8 (i.e., “No” in Step S1105),the memory control section 602 judges whether the operation ofoutputting image data to the hard disk drive 605 is performed (StepS1107). When the image data outputting operation is not performed (i.e.,“No” in Step S1107), it is judged whether the memory access permissionsignal should be output (Step S1112).

On the contrary, when the image data outputting operation is performedto the hard disk drive 605 (i.e., “Yes” in Step S1107), it is judgedwhether ΔC′ is not less than V5 (Step S1108). When ΔC′ is not less thanV5 (i.e., “Yes” in Step S1108), a transfer memory access mask signal ismade to be active so as to stop an output of image data (Step S1110).When ΔC′ is not greater than V5 (“No” in Step S1108), it is judgedwhether or not ΔC′ is not less than V6 (Step S1109). When ΔC′ is notless than V6 (“Yes” in Step S1109), it is judged whether the memoryaccess permission signal should be output without masking the transferaccess signal (Step S1112).

In addition, when ΔC′ is less than V6 (i.e., “No” in Step S1109), theprocess of making the transfer demand mask signal active and the processof masking the transfer demand signal are continuously performed (StepsS1110 and S1111). When the transfer demand signal is input to the memorycontrol section 602 without being masked, the memory control section 602judges whether the condition such that the transfer access permissionsignal can be output according to the transfer access demand signal issatisfied (Step S1112).

The processes in Steps S1110 to S1116 are performed similarly to thosein Steps S1010 to 1016 mentioned above with respect to FIG. 10.

According to the first embodiment mentioned above, the differencebetween the quantity of image data, which are input to the image memory603, and the quantity of image data, which are output to the hard diskdrive 605 from the image memory 603 is determined, and then thedifference is compared with the four values, i.e., a first, second,third and fourth value. When the difference reaches a value not greaterthan the first value, the process in which image data are output fromthe image memory 603 to the hard disk drive 605 is stopped. When thedifference reaches a value not less than the second value, the imagedata outputting process is started again. By performing this process,the image processing apparatus of the first embodiment can smoothlyperform the process, in which image data input are transferred in theapparatus, when the image data are input.

When the difference reaches a value not less than the third value or avalue not greater than the fourth value, an error signal is output tostop the system. By performing this process, the image processingapparatus of first embodiment can prevent the image data, which arestored in the image memory 603 but are not yet output to the hard disk605, from being lost when the image data are input. In addition, systemerrors such as an error such that the data quantity difference isdetermined as a negative value can be detected.

Further, according to the first embodiment, the difference between thequantity of image data input from the hard disk drive 605 to the imagememory 603 and the quantity of image data output from the image memory603 to the outside is determined, and then the difference is comparedwith four values, i.e., a fifth, sixth, seventh and eighth value. Whenthe difference reaches a value not greater than the fifth value, theprocess in which image data are output from the image memory 603 to thehard disk drive 605 is stopped. When the difference reaches a value notless than the sixth value, the image data outputting process is startedagain. By performing this process, the image processing apparatus of thefirst embodiment can smoothly perform the process, in which the imagedata transmitted from the inside of the apparatus are output to theoutside, when image data are input.

When the difference reaches a value not less than the seventh value or avalue not greater than the eighth value, an error signal is output tostop the system. By performing this process, the image processingapparatus of first embodiment can prevent the image data, which arestored in the image memory 603 but are not yet output to the outside,from being lost when the image data are output. In addition, systemerrors such as an error such that the data quantity difference isdetermined as a negative value can be detected.

Second Embodiment

Next, the second embodiment of the image processing apparatus of thepresent invention will be explained. The image processing apparatus ofthe second embodiment has a configuration similar to those of the imageprocessing apparatus of the first embodiment and the image formingapparatus to which the image processing apparatus of the firstembodiment is applied. Therefore, in the second embodiment, explanationor illustration of the devices similar to those in the first embodimentare omitted, and only the points different from the first embodimentwill be hereinafter explained.

FIG. 12 is a view for explaining the configuration of the imageprocessing apparatus of the second embodiment. As shown in FIG. 12, inthe process in which image data are input to the image memory 603 andthe image data are output from the image memory 603 to the hard diskdrive 605, variation in the quantity of the image data stored in theimage memory 603 is detected. The maximum value in the variation isrecorded for each predetermined page, and the preliminarily-set thirdvalue is renewed according to the recorded maximum value.

Namely, the image processing apparatus of the second embodiment has adifference recording section 1201, which records in order thedifferences in line number between the external input line number C1 andthe internal output line number C2, which are calculated by thedifference calculation section 701. The difference recording section1201 records the differences for each predetermined page, and outputsthe differences to the line setting section 702. The line settingsection 702 outputs the differences recorded by the difference recordingsection 1201 to the system control section 323.

The line number differences in each predetermined page change with alapse of time. The system control section 323 detects a maximum value(hereinafter referred to as a maximum variation value) of thedifferences recorded for each predetermined page, and outputs themaximum variation value to the line setting section 702. The linesetting section 702 outputs the maximum variation value input by thesystem control section 323 to the difference comparison section 703. Thedifference comparison section 703 sets the maximum variation value as anew third value. By performing the above-mentioned operations, thepreliminarily-set third value is renewed with the maximum variationvalue when image data in each predetermined page are processed.

In addition, the difference recording section 1201 records in order theline number differences which are calculated by the differencecalculation section 701, when the image processing apparatus outputs theimage data from the image memory 602. The recorded line numberdifferences are output to the line setting section 702. The line settingsection 702 outputs the line number differences recorded by thedifference recording section 1201 to the system control section 323. Thesystem control section 323 sets the maximum variation value as a newthird value by the same method as the method mentioned above in theimage data inputting process.

FIGS. 13A to 13C are view for explaining the processes performed in theimage processing apparatus of the second embodiment. Specifically, FIGS.13A to 13C are view for explaining how the third value is renewedreferring to a case in which image data are input from outside to thememory control section 602. FIG. 13A illustrates the total quantity ofimage data being access to the image memory 603 in the image inputoperation. FIGS. 13B and 13C illustrate the states of an accessedaddress in the image memory 603. The flows of image data indicated byimage data A and image data B in FIGS. 13C to 13C correspond to theflows of image transfer indicated by A and B in FIG. 1, respectively.

The accessed address in the image memory 603 changes its state forexample, from a state (b) to a state (c) with a lapse of time. In such acase, the image processing apparatus of the second embodiment detects amaximum value of the differences between the image data A and the imagedata B for the predetermined page. Then the third value (V3), which ispreliminarily set, is substituted by this maximum value for use thevalue in the next image processing.

By performing the above-mentioned operations, the image memory 603 inthe image processing apparatus of the second embodiment merely keeps animage storage memory space for preventing lost of image data due tooverwriting. The residual space in the image memory 603 can be used forother processes. Therefore the image memory 603 can be efficiently usedin the image processing apparatus of the second embodiment.

FIG. 14 is a flowchart for explaining the processes performed in theimage processing apparatus of the second embodiment. In the imageprocessing apparatus of the second embodiment, at first it is judgedwhether input of image data is started (Step S1401). When it is judgedthat the input of image data is started (i.e., “Yes” in Step 1401), thememory control section 602 performs the inputting process of inputtingimage data to the image memory while recording the variation in theimage data in the image memory 603. When it is judged that the input ofimage data is not yet started (i.e., “No” in Step S1401), the memorycontrol section 602 waits until the input of image data is started.

In addition, the memory control section 602 communicates with the systemcontrol section 323 to judge whether the image data of a predeterminedpage (i.e., the first page in the second embodiment) of an original areinput to the hard disk drive 605 (Step S1403). When the image data ofthe predetermined page (i.e., the first page in the second embodiment)of the original is not yet input (i.e., “No” in Step S140), the imagedata inputting processes of from S1402 and S1403 are repeated.

When it is judged that all the image data of the predetermined page arefinished in Step S1403, the system control section 323 detects a maximumvalue ΔM among the recorded image data (Step S1404). Then the linesetting section 702 communicates with the system control section 323 toinput the value ΔM as the line number of the image data. Then thepreliminarily-set third value is renewed with the value ΔM (Step S1405).Thus, all the processes are finished.

Although a processing for inputting image data to an image memory fromoutside alone is described in the above-described second embodiment, thepresent invention is not limited to an image inputting processing, butincludes processing for outputting image data to outside from an imagememory.

Third Embodiment

Next, a third embodiment of the present invention will be describedbelow. An image forming apparatus including an image processingapparatus of the third embodiment has the same constitution as for theimage forming apparatus to which the image processing apparatusaccording to the first embodiment is applied. Therefore, a part of theimage forming apparatus in diagrams and its partial description areomitted in the third embodiment.

Referring to FIG. 15, there is shown a diagram explaining a memorysection 322 of an image processing apparatus of the third embodiment.The memory section 322 of the image processing apparatus of the thirdembodiment stores image data, reads out the stored image data, and thenoutputs it with a line synchronizing signal.

The memory section 322 of the image processing apparatus of the thirdembodiment includes a hard disk drive (HD) 1104, which is a secondarymemory device for storing image data, an image cut out section 1105 forcutting out the image data read out after being stored in the hard diskdrive 1104 in a area corresponding to a predetermined area of an imageformed on the basis of the read-out image data, an image memory 1106,which is a primary memory device into which the cut out image data iswritten, and a memory control section 1102 for controlling readingprocessing for reading out the image data from the hard disk drive 1104and transferring processing for transferring the cut out image data tothe image memory 1106. The secondary memory device is not limited to thehard disk, but it can be a magnetic disk unit such as a MO.

The memory section 322 of the image processing apparatus of the thirdembodiment further includes a compression and decompression section 1103for compressing image data before being stored in the hard disk drive1104 and decompressing image data read out from the hard disk drive 1104and an image data decompressing section for decompressing image dataread out from the primary memory device by the image data readingsection.

The memory control section 1102 can change the range of the image datacut out by the image cut out section 1105 per units of the minimum imagedata amount that can be transferred. All of an image input/outputsection 1101, the memory control section 1102, the compression anddecompression section 1103, and the image cut out section 1105 of thethird embodiment include a CPU and a logic circuit.

In the above constitution, the memory control section 1102 communicateswith a system control section 323 to receive commands from the systemcontrol section 323. The commands include commands related to an inputor output of image data, commands related to compression ordecompression, and commands related to cutting out and they aretransmitted to each part of the memory section 322 according to eachcontent.

Referring to FIG. 16, there is shown a block diagram for explaining aconstitution of the memory control section 1102. The memory controlsection 1102 includes an arbiter 705, an input/output image addresscounter 1202, a transfer image address counter 1203, an address selector1204, and an access control circuit 1205.

The arbiter 1201 has a constitution for outputting a transfer accessenabling signal “o”. The arbiter 1201 outputs the transfer accessenabling signal “o” when an input/output memory access signal “l” isnon-active and a transfer memory access signal “m” is active.

The input/output image address counter 1202 is an address counterincremented in response to an input memory access signal “l” and outputsa memory address at which an input image data is stored in the imagememory 1106. The transfer image address counter 1203 is an addresscounter incremented in response to a transfer access signal “m” andoutputs a memory address at which the image data is stored in the harddisk drive 1104. Both of the input/output image address counter 1202 andthe transfer image address counter 1203 are initialized once to apredetermined value at a start of a memory access.

The address selector 1204 is a selector for selecting one of theinput/output image data and the transfer image data according to asignal “u” output by the arbiters 1201. The access control circuit 1205divides an input physical address into a row address and a columnaddress corresponding to a DRAM which is included in the image memory1106 on the basis of a signal input from the address selector. Then, itoutputs them to an 11-bit address bus 1206. In addition, the accesscontrol circuit outputs a DRAM control signals according to a signalinput from the arbiter 1201.

The image input/output section 1101 communicates with the memory controlsection 1102 to receive commands from the memory control section 1102.Then, it operates according to a received command. In addition, itoutputs status information for notifying an image data input/outputstate to the memory control section 1102.

When receiving an image input command from the memory control section1102, the image input/output section 1101 outputs image data (inputimage data) input together with various synchronizing signals in unitsof 8 pixels with an input-output memory access signal “l”. Whenreceiving an image output command from the memory control section 1102,the image input/output section 110 outputs image data input via thememory control section 1102 with various synchronizing signals.

The compression and decompression section 1103 communicates with thememory control section 1102 to receive commands from the memory controlsection 1102 and operates according to a received command. In addition,it outputs status information for notifying an image data compressionand decompression state to the memory control section 1102. Whenreceiving a compression command, the compression and decompressionsection 1103 outputs a transfer memory access signal “m” for requestingthe memory control section 1106 to transfer the decompressed image data.

When the compression and decompression section 1103 inputs a transfermemory access permission signal “o” from the memory control section1102, decompressed image data is output to the image memory 1106 via thememory control section 1102. When receiving a compression command, thecompression and decompression section 1103 outputs a transfer accessrequest signal “m” and inputs image data via the memory control section1102 if the transfer memory access permission signal “o” is active.Then, it compresses the input image data and stores it into the harddisk drive 1104.

In addition, the compression and decompression section 1103 communicateswith the memory control section 1102 to give an instruction on cuttingout the decompressed image data. At this time, the compression anddecompression section 1103 outputs the decompressed image data to theimage cut out section 1105. At this time, the memory control section1102 outputs a control signal “q” to the image cut out section 1105 andgives an instruction on addresses of image data corresponding to a startpoint and an end point of the image to be cut out.

The image cut out section 1105 cuts out image data input from thecompression and decompression section 1103 on the basis of the controlsignal input from the memory control section 1102. The cut out imagedata is input to the image memory 1106 via the memory control section1102. In addition, the image cut out section 1105 communicates with thememory control section 1102 to output status information indicating animage data transfer processing state to the memory control section 1102.

The image memory 1106 includes a semiconductor memory element such as aDRAM. The image memory 1106 has a 2M-byte storage capacity so as tostore binary image data having an A4 size at 400 dpi.

The image input/output section 1101 inputs image data from an IPU 312.At this time, the image data is input with various synchronizing signalsshown in FIG. 5. The input image data is input to the compression anddecompression section 1103 via the memory control section 1102 to bedecompressed and then stored once into the hard disk drive (HD) 1104. Inthis operation, the image memory 1102 is used as a buffer.

The image processing apparatus according to the third embodiment has afunction of image division. An operation for reading image data storedin the hard disk drive 1104 will be described below for an operationwith an image division and an operation without an image division (anormal operation).

1. Normal Operation

If image data is read out to form an image in a normal operation, theimage data is decompressed in the compression and decompression section1103 and output to the image memory 1106 via the memory control section1102. Then, it is stored in the image memory 1106 and input to a printercontrol section 345 via the image input/output section 1101.

2. Operation with Image Division

If the image division is executed, image data is decompressed in thecompression and decompression section 1103 in the same manner as for thenormal operation. For the image division, the memory control section1102 communicates with the compression and decompression section 1103and the image cut out section 1106 to enable a control signal for givingan instruction on image cutting-out processing. In addition, itspecifies a size of an image to be cut out with the control signal “q”and a start point and an end point for the cutting.

The start point, the end point, and the image size are arbitrarilychangeable per units of the minimum data amount of image data that canbe transferred from the image cut out section 1105 to the image memory1106.

The image cut out section 1105 divides the image data at addressescorresponding to the designated start and end points and outputs it tothe image memory 1106 with the memory address “p” via the memory controlsection 1102. The designated image data is input to the image memory1106 and stored at the address designated with the memory address “p”.Additionally it is input to the printer control section 345 via theimage input/output section 1101. An image forming section 330 forms animage based on the divided image data. As a result, an image is formedand is cut out at the start and end points designated with the controlsignal “q”.

Referring to FIG. 17A and FIG. 17B, there are shown diagrams explaininga cut out image (divided image data). FIG. 17A schematically shows astate of the image data read from the hard disk drive 1104 andtransferred to the image cut out section 1105. FIG. 17B schematicallyshows a state of the image data cut out in the image cut out section1105 and transferred to the image memory 1106.

The image data read from the hard drive 1104 consists of lines startingat Ps as shown in FIG. 17A, with the line having a length of a singleline in a main scanning direction. The image data shown in FIG. 17A isfor forming an image of a sheet of an original document.

The image data cut out in the image cut out section 1105 is cut out asshown in FIG. 17B from the image data shown in FIG. 17A so as to cut outan image Q having a length X in the main scanning direction and a lengthY in the sub-scanning direction from a sheet of a document image. Atthis point, the image P is discarded. In the third embodiment, the imagedata is cut out before being stored in the image memory 1106, andtherefore the image memory need not have a capacity of storing a sheetof an original document, which is advantageous to downsize the imagememory 1106.

Furthermore, the reduction of the capacity used for storing image datain the storage capacity of the image memory 1106 enables a storagecapacity, which is not used for storing the image data, to be used forother processing (a rotation of an image, for example) so as to utilizethe image memory 1106 effectively.

Referring to FIG. 18, there is shown a flowchart explaining imagedivision processing executed in the image processing apparatus accordingto the third embodiment. The image processing apparatus according to thethird embodiment judges whether or not image data is requested to beread out (Step S1401). If the image data is judged to be requested to beread out (S1401: Yes), it is judged whether or not an image division isexecuted (Step S1402). The image cut out section 1105 inputs a startpoint, an end point, and a size of an image to be cut out from thememory control section 1102 (Step S1403) and executes the imagecutting-out processing (Step S1404).

Then, the image data of the cut out image is transferred to the imagememory 1106 and output to the printer and the processing is terminated.On the other hand, if the image data is judged not to be requested to beread out in step S1401 (S1401: No), the control is put in a standbystate until a readout request is issued. If the image division is judgednot to be executed in Step S1402 (S1402: No), the read image data isoutput to the printer without image division processing.

The mechanisms and processes set forth in the present description may beimplemented using one or more conventional general purposemicroprocessors programmed according to the teachings in the presentspecification, as will be appreciated to those skilled in the relevantart(s). Appropriate software coding can readily be prepared by skilledprogrammers based on the teachings of the present disclosure, as willalso be apparent to those skilled in the relevant art(s). However, aswill be readily apparent to those skilled in the art, the presentinvention also may be implemented by the preparation ofapplication-specific integrated circuits or by interconnecting anappropriate network of conventional component circuits.

The present invention thus also includes a computer-based product whichmay be hosted on a storage medium and include instructions which can beused to program a microprocessor to perform a process in accordance withthe present invention. This storage medium can include, but is notlimited to, any type of disk including floppy disks, optical disks,CD-ROMs, magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, flashmemory, magnetic or optical cards, or any type of media suitable forstoring electronic instructions.

The present invention is not limited to the above embodiments. In otherwords, while the image processing apparatus of the present invention isa digital image forming apparatus in the first and third embodiments,the image processing apparatus of the present invention can be any of aprinter, a copying machine, and a facsimile.

Numerous additional modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, thepresent invention may be practiced otherwise than as specificallydescribed herein.

The present invention claims priority and contains subject matterrelated to Japanese Patent Application Nos. 11-271330, filed on Sep. 24,1999 and 2000-284293, filed on Sep. 19, 2000, and the entire contents ofboth of which are incorporated by reference herein.

1. An image processing apparatus provided with a primary memory deviceand a secondary memory device both having image data memorized therein,in which said image data are input to said primary memory device, theapparatus comprising: an external input data amount acquisition deviceacquiring the amount of said image data input to said primary memorydevice; an internal output data amount acquisition device acquiring theamount of said image data output from said primary memory device andinput to said secondary memory device; a first difference data amountcalculation device subtracting the amount of the data acquired by saidinternal output data amount acquisition device from the amount of thedata acquired by said external input data amount acquisition device, andcalculating first difference data amount by the subtraction; a memoryaccess control device practicing the inputting and outputting of saidimage data with time sharing in said primary memory device, comparingsaid first difference data amount with a first value and a second valuelarger than said first value, stopping the processing of outputting saidimage data from said primary memory device to said secondary memorydevice when said first difference data amount reaches the value equal toor smaller than said first value, and starting again the processing ofoutputting said image data from said primary memory device to saidsecondary memory device when said first difference data amount reachesthe value equal to or larger than said second value; and an error signaloutputting device comparing said first difference data amount with athird value larger than said second value and a fourth value smallerthan said first value, and outputting an error signal when said firstdifference data amount reaches the value equal to or larger than saidthird value or when said first difference data amount reaches the valueequal to or smaller than said fourth value.
 2. The image processingapparatus as defined in claim 1, wherein said image processing apparatusfurther comprises: a variation amount recording device detecting thevariation amount of said first difference data and recording the maximumvalue of said variation amount per unit of the predetermined pagesnumber; and a set value renewal device renewing said third valuepreviously set on the basis of the maximum value of the variation amountrecorded by said variation amount recording device.
 3. The imageprocessing apparatus as defined in claim 1, wherein said primary memorydevice inputs and outputs in order said image data line by line with themethod of raster; and wherein said external input data amountacquisition device and said internal output data amount acquisitiondevice acquire the amount of said image data as the number of lines. 4.The image processing apparatus as defined in claim 2, wherein saidprimary memory device inputs and outputs in order said image data lineby line with the method of raster; and wherein said external input dataamount acquisition device and said internal output data amountacquisition device acquire the amount of said image data as the numberof lines.
 5. The image processing apparatus as defined in claim 1,wherein said image processing apparatus further comprises: an image datacompression device compressing said image data before being memorized insaid secondary memory device; and an image data decompression devicedecompressing said image data after being read out from said secondarymemory device by said image data reading-out device.
 6. The imageprocessing apparatus as defined in claim 1, wherein said secondarymemory device is a magnetic disc apparatus.
 7. The image processingapparatus as defined in claim 1, wherein said primary memory device is amemory constructed with a semiconductor.
 8. The image processingapparatus as defined in claim 1, wherein said memory access controldevice previously inputs said image data of the amount corresponding tosaid first value to said primary memory device from outside, prior tothe outputting of said image data to said secondary memory device fromsaid primary memory device.
 9. The image processing apparatus as definedin claim 1, wherein said error signal outputting device outputs theerror signal only during the time period of practicing the process ofoutputting said image data to said secondary memory device from saidprimary memory device.
 10. The image processing apparatus as defined inclaim 2, wherein said memory access control device previously inputssaid image data of the amount corresponding to said first value to saidprimary memory device from outside, prior to the outputting of saidimage data to said secondary memory device from said primary memorydevice.
 11. The image processing apparatus as defined in claim 2,wherein said error signal outputting device outputs the error signalonly during the time period of practicing the process of outputting saidimage data to said secondary memory device from said primary memorydevice.
 12. The image processing apparatus as defined in claim 3,wherein said memory access control device previously inputs said imagedata of the amount corresponding to said first value to said primarymemory device from outside, prior to the outputting of said image datato said secondary memory device from said primary memory device.
 13. Theimage processing apparatus as defined in claim 3, wherein said errorsignal outputting device outputs the error signal only during the timeperiod of practicing the process of outputting said image data to saidsecondary memory device from said primary memory device.
 14. The imageprocessing apparatus as defined in claim 8, wherein said error signaloutputting device outputs the error signal only during the time periodof practicing the process of outputting said image data to saidsecondary memory device from said primary memory device.
 15. An imageprocessing apparatus provided with a primary memory device and asecondary memory device both having image data memorized therein, inwhich said image data are output to outside from said primary memorydevice, the apparatus comprising; an internal input data amountacquisition device acquiring the amount of said image data input to saidprimary memory device from said secondary memory device; an externaloutput data amount acquisition device acquiring amount of said imagedata output to outside from said primary memory device; a seconddifference data amount calculation device subtracting the amount of thedata acquired by said external output data amount acquisition devicefrom the amount of the data acquired by said internal input data amountacquisition device, and calculating second difference data amount by thesubtraction; a memory access control device practicing the inputting andoutputting of said image data with time sharing in said primary memorydevice, comparing said second difference data amount with a fifth valueand a sixth value larger than said fifth value, stopping the processingof outputting said image data from said primary memory device to saidsecondary memory device when said second difference data amount reachesthe value equal to or larger than said fifth value, and starting againthe processing of outputting said image data from said primary memorydevice to said secondary memory device when said second difference dataamount reaches the value equal to or smaller than said sixth value; andan error signal outputting device comparing said second difference dataamount with a seventh value larger than said sixth value and a eighthvalue smaller than said fifth value, and outputting an error signal whensaid second difference data amount reaches the value equal to or largerthan said seventh value or when said second difference data amountreaches the value equal to or smaller than said eighth value.
 16. Theimage processing apparatus as defined in claim 15, wherein said memoryaccess control device previously inputs said image data of the amountcorresponding to said fifth value to said primary memory device fromsaid secondary memory device, prior to the outputting of said image datafrom said primary memory device.
 17. The image processing apparatus asdefined in claim 15, wherein said error signal outputting device outputsthe error signal only during the time period of practicing theprocessing of outputting said image data to outside from said primarymemory device.
 18. The image processing apparatus as defined in claim15, wherein said image processing apparatus further comprises: avariation amount recording device detecting the variation amount of saidsecond difference data only during the time period of practicing theprocessing of outputting said image data from said primary memorydevice, and recording the maximum value of the variation amount per unitof the predetermined pages number; and a set value renewal devicerenewing said seventh value previously set on the basis of the maximumvalue of the variation amount recorded by said variation amountrecording device.
 19. The image processing apparatus as defined in claim15, wherein said primary memory device inputs and outputs in order saidimage data with the method of raster; and wherein said internal inputdata amount acquisition device and said external output data amountacquisition device acquire the amount of said image data as the linesnumber.
 20. The image processing apparatus as defined in claim 16,wherein said error signal outputting device outputs the error signalonly during the time period of practicing the processing of outputtingsaid image data to outside from said primary memory device.
 21. Theimage processing apparatus as defined in claim 16, wherein said imageprocessing apparatus further comprises: a variation amount recordingdevice detecting the variation amount of said second difference dataonly during the time period of practicing the processing of outputtingsaid image data from said primary memory device, and recording themaximum value of the variation amount per unit of the predeterminedpages number; and a set value renewal device renewing said seventh valuepreviously set on the basis of the maximum value of the variation amountrecorded by said variation amount recording device.
 22. The imageprocessing apparatus as defined in claim 16, wherein said primary memorydevice inputs and outputs in order said image data with the method ofraster; and wherein said internal input data amount acquisition deviceand said external output data amount acquisition device acquire theamount of said image data as the lines number.
 23. The image processingapparatus as defined in claim 17, wherein said image processingapparatus further comprises: a variation amount recording devicedetecting the variation amount of said second difference data onlyduring the time period of practicing the processing of outputting saidimage data from said primary memory device, and recording the maximumvalue of the variation amount per unit of the predetermined pagesnumber; and a set value renewal device renewing said seventh valuepreviously set on the basis of the maximum value of the variation amountrecorded by said variation amount recording device.
 24. The imageprocessing apparatus as defined in claim 17, wherein said primary memorydevice inputs and outputs in order said image data with the method ofraster; and wherein said internal input data amount acquisition deviceand said external output data amount acquisition device acquire theamount of said image data as the lines number.
 25. The image processingapparatus as defined in claim 18, wherein said primary memory deviceinputs and outputs in order said image data with the method of raster;and wherein said internal input data amount acquisition device and saidexternal output data amount acquisition device acquire the amount ofsaid image data as the lines number.
 26. An image processing methodapplicable to an image processing apparatus provided with a primarymemory device and a secondary memory device both having image datamemorized therein, in which said image data are input to said primarymemory device from outside, the method comprising the steps of: anexternal input data amount acquisition process of acquiring the amountof said image data input to said primary memory device from outside; aninternal output data amount acquisition process of acquiring the amountof said image data output from said primary memory device and input tosaid secondary memory device; a first difference data amount calculationprocess of subtracting the amount of the data acquired in said internaloutput data amount acquisition process from the amount of the dataacquired in said external input data amount acquisition process, andcalculating first difference data amount by the subtraction; a memoryaccess control process of practicing the inputting and outputting ofsaid image data with time sharing in said primary memory device,comparing said first difference data amount with a first value and asecond value larger than said first value, stopping the processing ofoutputting said image data from said primary memory device to saidsecondary memory device when said first difference data amount reachesthe value equal to or smaller than said first value, and starting againthe processing of outputting said image data from said primary memorydevice to said secondary memory device when said first difference dataamount reaches the value equal to or larger than said second value; andan error signal outputting process of comparing said first differencedata amount with a third value larger than said second value and afourth value smaller than said first value, and outputting an errorsignal when said first difference data amount reaches the value equal toor larger than said third value or when said first difference dataamount reaches the value equal to or smaller than said fourth value. 27.The image processing method as defined in claim 26, further comprisingthe step of: a setting process of setting said first value, said secondvalue, said third value, and said fourth value, all to be compared withsaid first difference data amount.
 28. The image processing method asdefined in claim 26, further comprising the steps of: a variation amountrecording process of detecting the variation amount of said firstdifference data and recording the maximum value of said variation amountper unit of the predetermined pages number; and a set value changingprocess of changing said third value previously set on the basis of themaximum value of the variation amount recorded in said variation amountrecording process.
 29. The image processing method as defined in claim26, wherein said primary memory device inputs and outputs in order saidimage data line by line with the method of raster; and wherein, in saidexternal input data amount acquisition process and said internal outputdata amount acquisition process, the amount of said image data areacquired as the number of lines.
 30. The image processing method asdefined in claim 26, wherein said image processing method furthercomprises the steps of: an image data compression process of compressingsaid image data before memorizing said image data in said secondarymemory device; and an image data decompression process of decompressingsaid image data after reading out said image data from said secondarymemory device by said image data reading-out device.
 31. The imageprocessing method as defined in claim 26, wherein, in said memory accesscontrol process, said image data of the amount corresponding to saidfirst value are previously input to said primary memory device fromoutside, prior to the outputting of said image data to said secondarymemory device from said primary memory device.
 32. The image processingmethod as defined in claim 26, wherein, in said error signal outputtingprocess, the error signal is output only during the time period ofpracticing the process of outputting said image data to said secondarymemory device from said primary memory device.
 33. The image processingmethod as defined in claim 27, further comprising the steps of: avariation amount recording process of detecting the variation amount ofsaid first difference data and recording the maximum value of saidvariation amount per unit of the predetermined pages number; and a setvalue changing process of changing said third value previously set onthe basis of the maximum value of the variation amount recorded in saidvariation amount recording process.
 34. The image processing method asdefined in claim 28, wherein, in said memory access control process,said image data of the amount corresponding to said first value arepreviously input to said primary memory device from outside, prior tothe outputting of said image data to said secondary memory device fromsaid primary memory device.
 35. The image processing method as definedin claim 28, wherein, in said error signal outputting process, the errorsignal is output only during the time period of practicing the processof outputting said image data to said secondary memory device from saidprimary memory device.
 36. The image processing method as defined inclaim 29, wherein, in said memory access control process, said imagedata of the amount corresponding to said first value are previouslyinput to said primary memory device from outside, prior to theoutputting of said image data to said secondary memory device from saidprimary memory device.
 37. The image processing method as defined inclaim 29, wherein, in said error signal outputting process, the errorsignal is output only during the time period of practicing the processof outputting said image data to said secondary memory device from saidprimary memory device.
 38. The image processing method as defined inclaim 31, wherein, in said error signal outputting process, the errorsignal is output only during the time period of practicing the processof outputting said image data to said secondary memory device from saidprimary memory device.
 39. An image processing method applicable to animage processing apparatus provided with a primary memory device and asecondary memory device both having image data memorized therein, inwhich said image data are output to outside from said primary memorydevice, the method comprising the steps of: an internal input dataamount acquisition process of acquiring the amount of said image datainput from said secondary memory device to said primary memory device;an external output data amount acquisition process of acquiring theamount of said image data output from said primary memory device tooutside; a second difference data amount calculation process ofsubtracting the amount of the data acquired in said external output dataamount acquisition process from the amount of the data acquired in saidinternal input data amount acquisition process, and calculating seconddifference data amount by the subtraction; a memory access controlprocess of practicing the inputting and outputting of said image datawith time sharing in said primary memory device, comparing said seconddifference data amount with a fifth value and a sixth value larger thansaid fifth value, stopping the processing of outputting said image datafrom said primary memory device to said secondary memory device whensaid second difference data amount reaches the value equal to or largerthan said fifth value, and starting again the processing of outputtingsaid image data from said primary memory device to said secondary memorydevice when said second difference data amount reaches the value equalto or smaller than said sixth value; and an error signal outputtingprocess of comparing said second difference data amount with a seventhvalue larger than said sixth value and a eighth value smaller than saidfifth value, and outputting an error signal when said second differencedata amount reaches the value equal to or larger than said seventh valueor when said second difference data amount reaches the value equal to orsmaller than said eighth value.
 40. The image processing method asdefined in claim 39, wherein in said memory access control process, saidimage data of the amount corresponding to said fifth value arepreviously input to said primary memory device from said secondarymemory device, prior to the outputting of said image data from saidprimary memory device.
 41. The image processing method as defined inclaim 39, wherein said error signal outputting process comprises: a stepof outputting said error signal only during the time period ofpracticing the process of outputting said image data from said primarymemory device to outside.
 42. The image processing method as defined inclaim 39, comprising the steps of: a variation amount recording processof detecting the variation amount of said second difference data onlyduring the time period of practicing the process of outputting saidimage data from said primary memory device and recording the maximumvalue of said variation amount per unit of the predetermined pagesnumber; and a set value renewal process of renewing said seventh valuepreviously set on the basis of the maximum value of the variation amountrecorded in said variation amount recording process.
 43. The imageprocessing method as defined in claim 39, wherein said primary memorydevice inputs and outputs in order said image data line by line with themethod of raster; and wherein in said internal input data amountacquisition process and in said external output data amount acquisitionprocess, the amount of said image data are acquired as the number oflines.
 44. The image processing method as defined in claim 39, whereinsaid image processing method further comprises the steps of: an imagedata compression process of compressing said image data beforememorizing said image data in said secondary memory device; and an imagedata decompression process of decompressing said image data afterreading out said image data from said secondary memory device by saidimage data reading-out device.
 45. The image processing method asdefined in claim 40, wherein said error signal outputting processcomprises: a step of outputting said error signal only during the timeperiod of practicing the process of outputting said image data from saidprimary memory device to outside.
 46. The image processing method asdefined in claim 40, comprising the steps of: a variation amountrecording process of detecting the variation amount of said seconddifference data only during the time period of practicing the process ofoutputting said image data from said primary memory device and recordingthe maximum value of said variation amount per unit of the predeterminedpages number; and a set value renewal process of renewing said seventhvalue previously set on the basis of the maximum value of said variationamount recorded in said variation amount recording process.
 47. Acomputer readable recording medium for recording a program of causing acomputer to practice an image processing method applicable to an imageprocessing apparatus provided with a primary memory device and asecondary memory device both having image data memorized therein, inwhich said image data are input to said primary memory device fromoutside, wherein said computer readable recording medium records theprogram of causing said computer to practice the image processing methodcomprising the steps of: an external input data amount acquisitionprocess of acquiring the amount of said image data input to said primarymemory device from outside; an internal output data amount acquisitionprocess of acquiring the amount of said image data output from saidprimary memory device and input to said secondary memory device; a firstdifference data amount calculation process of subtracting the amount ofthe data acquired in said internal output data amount acquisitionprocess from the amount of the data acquired in said external input dataamount acquisition process, and calculating first difference data amountby the subtraction; a memory access control process of practicing theinputting and outputting of said image data with time sharing in saidprimary memory device, comparing said first difference data amount witha first value and a second value larger than said first value, stoppingthe processing of outputting said image data from said primary memorydevice to said secondary memory device when said first difference dataamount reaches the value equal to or smaller than said first value, andstarting again the processing of outputting said image data from saidprimary memory device to said secondary memory device when said firstdifference data amount reaches the value equal to or larger than saidsecond value; and an error signal outputting process of comparing saidfirst difference data amount with a third value larger than said secondvalue and a fourth value smaller than said first value, and outputtingan error signal when said first difference data amount reaches the valueequal to or larger than said third value or when said first differencedata amount reaches the value equal to or smaller than said fourthvalue.
 48. The computer readable recording medium as defined in claim47, wherein said recording medium records the program of causing saidcomputer to practice said image processing method further comprising thestep of: a setting process of setting said first value, said secondvalue, said third value, and said fourth value to be compared with saidfirst difference data amount.
 49. The computer readable recording mediumas defined in claim 47, wherein said recording medium records theprogram of causing said computer to practice said image processingmethod further comprising the steps of: a variation amount recordingprocess of detecting the variation amount of said first difference dataand recording the maximum value of said variation amount per unit of thepredetermined pages number; and a set value renewal process of renewingsaid third value previously set on the basis of the maximum value ofsaid variation value recorded in said variation amount recordingprocess.
 50. The computer readable recording medium as defined in claim47, wherein said recording medium records the program of causing saidcomputer to practice said image processing method further comprising:wherein said primary memory device inputs and outputs in order saidimage data line by line with the method of raster; and wherein saidexternal input data amount acquisition device and said internal outputdata amount acquisition device acquire the amount of said image data asthe number of lines.
 51. The computer readable recording medium asdefined in claim 47, wherein said computer readable recording mediumrecords the program of causing said computer to practice the imageprocessing method further comprises the steps of: an image datacompression process of compressing said image data before memorizingsaid image data in said secondary memory device; and an image datadecompression process of decompressing said image data after reading outsaid image data from said secondary memory device by said image datareading-out device.
 52. The computer readable recording medium asdefined in claim 47, wherein, in said memory access control process,said recording medium records the program of causing said computer topractice the image processing method of previously inputting said imagedata of the amount corresponding to said first value to said primarymemory device from outside, prior to the outputting of said image datato said secondary memory device from said primary memory device.
 53. Thecomputer readable recording medium as defined in claim 47, wherein, insaid error signal outputting process, said recording medium records theprogram of causing said computer to practice the image processing methodof outputting the error signal only during the time period of practicingthe process of outputting said image data to said secondary memorydevice from said primary memory device.
 54. The computer readablerecording medium as defined in claim 48, wherein said recording mediumrecords the program of causing said computer to practice said imageprocessing method further comprising the steps of: a variation amountrecording process of detecting the variation amount of said firstdifference data and recording the maximum value of said variation amountper unit of the predetermined pages number; and a set value renewalprocess of renewing said third value previously set on the basis of themaximum value of said variation value recorded in said variation amountrecording process.
 55. The computer readable recording medium as definedin claim 49, wherein, in said error signal outputting process, saidrecording medium records the program of causing said computer topractice the image processing method of outputting the error signal onlyduring the time period of practicing the process of outputting saidimage data to said secondary memory device from said primary memorydevice.
 56. The computer readable recording medium as defined in claim49, wherein, in said memory access control process, said recordingmedium records the program of causing said computer to practice theimage processing method of previously inputting said image data of theamount corresponding to said first value to said primary memory devicefrom outside, prior to the outputting of said image data to saidsecondary memory device from said primary memory device.
 57. Thecomputer readable recording medium as defined in claim 50, wherein, insaid memory access control process, said recording medium records theprogram of causing said computer to practice the image processing methodof previously inputting said image data of the amount corresponding tosaid first value to said primary memory device from outside, prior tothe outputting of said image data to said secondary memory device fromsaid primary memory device.
 58. The computer readable recording mediumas defined in claim 50, wherein, in said error signal outputtingprocess, said recording medium records the program of causing saidcomputer to practice the image processing method of outputting the errorsignal only during the time period of practicing the process ofoutputting said image data to said secondary memory device from saidprimary memory device.
 59. The computer readable recording medium asdefined in claim 52, wherein, in said error signal outputting process,said recording medium records the program of causing said computer topractice the image processing method of outputting the error signal onlyduring the time period of practicing the process of outputting saidimage data to said secondary memory device from said primary memorydevice.
 60. A computer readable recording medium for recording a programof causing a computer to practice an image processing method applicableto an image processing apparatus provided with a primary memory deviceand a secondary memory device both having image data memorized therein,in which said image data are output to outside from said primary memorydevice, wherein said computer readable recording medium records theprogram of causing said computer to practice the image processing methodcomprising the steps of: an internal input data amount acquisitionprocess of acquiring the amount of said image data input to said primarymemory device from said secondary memory device; an external output dataamount acquisition process of acquiring the amount of said image dataoutput to outside from said primary memory device; a second differencedata amount calculation process of subtracting the amount of the dataacquired by said external output data amount acquisition device from theamount of the data acquired by said internal input data amountacquisition device, and calculating second difference data amount by thesubtraction; a memory access control process of practicing the inputtingand outputting of said image data with time sharing in said primarymemory device, comparing said second difference data amount with a fifthvalue and a sixth value larger than said fifth value, stopping theprocessing of outputting said image data from said primary memory deviceto said secondary memory device when said second difference data amountreaches the value equal to or larger than said fifth value, and startingagain the processing of outputting said image data from said primarymemory device to said secondary memory device when said seconddifference data amount reaches the value equal to or smaller than saidsixth value; and an error signal outputting process of comparing saidsecond difference data amount with a seventh value larger than saidsixth value and an eighth value smaller than said fifth value, andoutputting an error signal when said second difference data amountreaches the value equal to or larger than said seventh value or whensaid second difference data amount reaches the value equal to or smallerthan said eighth value.
 61. The computer readable recording medium asdefined in claim 60, wherein, in said memory access control process,said recording medium records the program of causing said computer topractice said image processing method of previously inputting said imagedata of the amount corresponding to said fifth value to said primarymemory device from said secondary memory device, prior to the outputtingof said image data from said primary memory device.
 62. The computerreadable recording medium as defined in claim 60, wherein, in said errorsignal outputting process, said recording medium records the program ofcausing said computer to practice said image processing method ofoutputting the error signal only during the time period of practicingthe process of outputting said image data to outside from said primarymemory device.
 63. The computer readable recording medium as defined inclaim 60, wherein said recording medium records the program of causingsaid computer to practice said image processing method furthercomprising the steps of: a variation amount recording process ofdetecting the variation amount of said second difference data onlyduring the time period of practicing the process of outputting saidimage data from said primary memory device; and a set value renewalprocess of renewing said seventh value previously set on the basis ofthe maximum value of said variation amount recorded in said variationamount recording process.
 64. The computer readable recording medium asdefined in claim 60, wherein said recording medium records the programof causing said computer to practice the image processing method, inwhich said primary memory device inputs and outputs in order said imagedata line by line with the method of raster and the amount of said imagedata is acquired as the lines number in said internal input data amountacquisition process and in said external output data amount acquisitionprocess.
 65. The computer readable recording medium as defined in claim61, wherein, in said error signal outputting process, said recordingmedium records the program of causing said computer to practice saidimage processing method of outputting the error signal only during thetime period of practicing the process of outputting said image data tooutside from said primary memory device.